A conventional data storage system enabling atomic transactions is disclosed in Japanese unexamined patent publication No. 2006-106868. This publication discloses that there are a log based scheme and a side-file based scheme in file management systems and the disadvantages of the shadow page technique used in the side-file based scheme and also discloses a file system capable of overcoming the disadvantages.
Many conventional atomic data storage systems have been structured like the file system in the disclosure. The publication mentions that the file system adopting the log based scheme is more advantageous; however, such a log based file system is expensive. In addition, the conventional file systems generally use a nonvolatile storage medium, such as a hard disk, to which a plurality of users access. While the users are using different files in the nonvolatile storage medium, if a user commits a file, the other files being processed by the other users could be occasionally committed in sync with the committed file. This situation causes unwanted data of the individual users to be stored upon a power failure, for example, which means one user can be affected by processing operations by the other users.